Bluetooth is a low-power, short-range wireless networking standard designed for local area voice and data transfer. Bluetooth radios operate in the unlicensed ISM band at 2.4 GHz with a set of 79 hop carriers with 1 MHz spacing. A master-slave communication model with frequency hopping spread spectrum (FHSS) transmission technique is adopted in the Bluetooth specification to ensure protection from interference and security of data. A collection of Bluetooth devices may be connected in an Ad Hoc fashion. The Bluetooth devices may connect to each other to form a network known as a piconet. One Bluetooth device may act as a master of the piconet, whereas the other devices may act as slaves. At the maximum, 8 active Bluetooth devices may participate in the one piconet. Time may be divided into slots of 625 us in the piconet. The master and slaves may alternate transmit opportunities in a time-division duplex (TDD) fashion. In particular, the master may transmit on available even numbered slots, as defined by the master's Bluetooth clock, while the slaves may transmit on available odd numbered slots. The master controls formation of Bluetooth communication links and communication procedures with slaves within the piconet. A slave may transmit only after being polled by the master.
Bluetooth supports various types of radio communication links including a Synchronous Connection-Oriented (SCO) link that reserves predetermined time slots on the time axis, and an Asynchronous Connection-less (ACL) link that randomly uses time slots on the time axis for communications. The ACL link is a so-called packet switching radio communications link where transmissions may be allowed in the slots not reserved for SCO links. The SCO link defined in the Bluetooth specification provides a full-duplex symmetric link between the master and a slave with reserved time slots. A data rate of 64 kbps is provided in both directions of the SCO link. The master transmits SCO packets in reserved master-to-slave SCO slots to the slave at regular SCO interval Tsco (counted in slots), and the slave is allowed to respond with SCO packets in reserved slave-to-master SCO slots even if the slave may not successfully decode the master's packet in the previous time slot. The slave-to-master SCO slots may directly follow the reserved master-to-slave SCO slots. No SCO packet retransmission occurs over the SCO link.
Bluetooth supports various types of SCO packets including HV1, HV2 and HV3. The SCO packets are typically used for 64 kb/s speech transmission with a fixed payload length of 240 bits. They differ from each other in terms of forward error correction code (FEC) rate used, for example, a rate ⅓ FEC is used for HV1 packet, a rate ⅔ FEC is used for HV2 packet, and no FEC is used for HV3 packet. A different SCO interval Tsco value may apply according to different SCO packet type. For example, Tsco=2 slots for HV1 packet, Tsco=4 slots for HV2 packet, and Tsco=6 slots for HV3 packet.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.